//
// Created by ASUS on 2024/3/14.
//
#include <bits/stdc++.h>
using namespace std;

//字符串分割
vector<string> split(string&s,char ch){
	vector<string> res;
	stringstream ss(s);
	string temp;
	while(getline(ss,temp,ch)) res.push_back(temp);
	return res;
}
//字符串拼接
string join(vector<string>&arr,string &ch){
	string res=arr[0];
	for(int i=1;i<arr.size();i++){
		res+=ch;
		res+=arr[i];
	}
	return res;
}

int main(){
	vector<string> ss{"a","b","cc","d_e"};

	auto s=join(ss,"");
	cout<<s<<endl;
	return 0;
}